Device and method for measurement of dispersed objects using fluorescent and non-fluorescent imaging with laser

This application claims priority under 35 USC 119(e) to provisional application No. 62/288,582 which was filed on Jan. 29, 2016.

The invention is related to federally sponsored research and development under US Department of Energy prime contract number DE-AC26-07NT42677, subcontract 12121-6301-03 entitled “Subsea Produced Water Sensor Development”, having subcontract dates Sep. 11, 2014 to Sep. 30, 2016.

The field of the invention is devices and methods for the measurement of the content of micrometer-scale objects in liquid or gas. Examples of the application include the measurement of oil and solids content in water produced from petroleum and natural gas reservoirs, measurement of oil or other objects in natural gas, detection and quantification of oil in ocean or other bodies of water, detection and quantification of droplets and solids in emissions to air, and measurement of other fluorescent and non-fluorescent microscale dispersed objects.

Measurement of microscale objects carried by fluid are represented by the following patents: U.S. Pat. Nos. 7,935,938 B2, 7,248,363 B2, 6,525,325 B1, European Patent No. EP 0 997 732 A1, U.S. Pat. Nos. 5,381,002, and 4,953,978. in addition, U.S. patent application Ser. No. 14/455,907 describes a system and a method for measuring oil content in water using 3-dimensional laser-induced fluorescence imaging.

The inventor has discovered that the certain types of dispersed material emits fluorescent light under excitation by laser light, which can be used to produce an image with a microscope. The inventor also discovered that the very short duration but high light energy of pulsed laser can be used to eliminate imaging blurring when the dispersed materials moves very fast, for example when the flowing liquid or gas has high velocity. The inventor also discovered that images of the same focal area can be formed with the excitation light, either with the reflected light or transmitted light, and the images can be compared with the fluorescence images to distinguish different types of dispersed objects, some with fluorescence and others without fluorescence. For example, oil droplets, which are fluorescent, can be distinguished from water-wet solid particles and gas bubbles which are not fluorescent. The inventor further discovered that the magnitude of fluorescence of the liquid or gas, which is captured in the fluorescence images, can be utilized to measure the amount of the dissolved materials that cause the fluorescence.

The present invention includes measurement devices and methods for using pulsed laser to produce simultaneous dual modal images, which are fluorescence images and excitation light images, of the objects in a flowing medium which may be liquid or gaseous. The images can be analyzed to determine the volume fractions of dispersed objects and distinguish different types of objects by comparing the images. The invention improves upon the prior art in several areas.

The present invention is a measurement device and method which utilize a pulsed laser to generate microscopic fluorescence and excitation light images of dispersed objects in liquid or gas, and analyze the images to determine the volume fractions of dispersed objects and distinguish different types of objects by comparing the images.

Firstly, the dual modal images greatly enhance the distinguishing of fluorescent objects (such as oil droplets) from non-fluorescent objects (such as solids and gas bubbles), which is important for accurate measurements of the different types of objects.

Secondly, the accuracy of the measurement can be preserved under much higher velocity of liquid or gas when comparing with 2-dimensional imaging methods in prior art. Pulsed lasers can provide sufficient light energy in much shorter pulse width than other types of light source. This can reduce the blurriness of images, and the errors in object volume calculations due to the blurriness, to negligible level even for very high velocity flows. Alternatively, continuous wave lasers can also be used along with cameras with sufficiently high frame rate or sufficiently short shutter time, to achieve the same reduction in image blurriness in high velocity flow situations. The apparatuses and methods disclosed herein can also be applied in situations where it is required for the dispersed objects to keep moving with the flow during the measurement.

FIG. 1 A Configuration for Fluorescence and Reflected Excitation Light Images

FIG. 2 A configuration such that the excitation light can be used to form transmitted light images

FIG. 3 A configuration for taking transmitted excitation fight images simultaneously with the fluorescence images

FIG. 4 A configuration for taking transmitted excitation fight images simultaneously with the fluorescence images

101 A conduit containing the mixture of the dispersed objects to be measured and the flowing carrier fluid

102 An imaging probe inserted into the mixture ( FIG. 1 )

103 A laser source

104 A fiber optic cable transmitting the laser from laser source 103 to probe 102

105 A camera capturing images of the dispersed objects with the fluorescence emitted by the objects

106 A camera capturing images of the dispersed objects with the laser light reflected by the objects

107 Power and data cables for controlling the cameras and downloading the images captured

108 An image processing unit, which is a computer at the site or at a remote location

109 A human-machine interface device for the user to control the device and to obtain the measurement results and other information from the device

201 An optical connector and beam expander assembly to prepare the laser light into the appropriate beam size

202 Excitation laser light

203 A beam splitter which both reflects light and transmits light

204 A dichromatic mirror

205 A microscopic objective

206 One of the dispersed objects to be measured

207 Fluorescence light emitted by the object 206

208 Light reflected by the object 206

209 Lens for the fluorescence image camera

210 Sensor to capture the fluorescence image

211 Lens for the excitation light image camera

212 Sensor to capture the excitation light image camera

302 Probe ( FIG. 3 )

306 Transmitted light ( FIG. 4 )

Configuration For Fluorescence and Reflected Excitation Light Images

A preferred configuration of the device and method is to take fluorescence and reflected excitation light images. The configuration is illustrated in FIG. 1 and FIG. 2 . Probe 102 for acquiring images of the objects to be measured is inserted into the pipe 101 which contains liquid or gas flowing in the direction of the arrow. The mixture of the liquid or gas, and the dispersed droplets, are illuminated with pulsed laser from laser source 103 . The laser light is also referred to as the excitation light in the description of the present invention. The probe contains a microscopic objective and other optical components for separating the fluorescent light induced by the laser and the reflected excitation light. The images are captured by cameras 105 and 106 , analyzed by computer 108 and reported to the user through an interface 109 .

Configuration For Fluorescence and Transmitted Excitation Light Images

In an alternative configuration as shown in FIG. 2 probe 302 is configured so that the excitation light can be used to form transmitted light images, which can be analyzed using the same approach as for reflected light images above.

FIGS. 3 and 4 illustrate a configuration for taking transmitted excitation light images simultaneously with the fluorescence images. The configuration is the similar to that for simultaneous fluorescence and reflected excitation light images. Camera 106 is positioned to the side opposite of object 206 with respect to objective 205 . Lens 211 focuses transmitted light 308 onto the image sensor 212 . The fluorescence images which are captured by camera 105 in this configuration are acquired in essentially the same manner as described for the configuration illustrated in FIG. 2 .

Variations of Configuration

The configuration can be varied for different applications without changing the principles of the invention. In one variation, the dispersed objects 205 move in vacuum confined by conduit 101 , or in a larger space where probe 102 and 302 are fixed.

In another configuration, the dispersed objects 206 are moved by conveyer belt or other non-flow mechanical devices.

In yet another configuration, the liquid or was carrying the dispersed objects are in a large space not confined by conduit 101 . For example, the carrier fluid is ocean water or atmosphere. The device is moved by a vehicle, with the optical end Probe 102 or 302 immersed in the fluid. The concentration of the dispersed objects are measured with the relative motion of the probe and the mixture of the fluid and dispersed objects.

In another configuration, the illumination laser light source is changed to a continuous wave laser. Imaging blurring is prevented by using the cameras with sufficiently high imaging frame rate or sufficiently short shutter time.

The above has disclosed the specifics of the present invention to measure dispersed objects in liquid or gas. It should be apparent to those skilled in the art that many other variations and modifications are possible which are within the spirit of the disclosed invention.